The present invention generally relates to electrochemical cells including anode and cathode additives and, more particularly, to alkaline electrochemical cells having cathodes formed of manganese dioxide and other additives, and anodes formed of zinc and other additives.
Conventional alkaline cells generally include a steel cylindrical can having a cathode comprising manganese dioxide as the active material and formed on the interior surface of the steel can, an anode comprising zinc powder and located in the center of the cell, a separator located between the anode and the cathode, and an alkaline electrolyte solution simultaneously contacting the anode, the cathode, and separator. A conductive current collector is commonly inserted into the anode active material and a seal assembly provides closure to the open end of the steel can.
A primary goal in designing alkaline battery cells is to increase the service performance of the cell. The service performance is the length of time for the cell to discharge under a given load to a specific voltage at which the cell is no longer useful for its intended purpose. One approach taken to increase service performance has been to increase the interior volume of the cell in order to increase the amount of active materials within the cell. However, the commercial external size of the cell is generally fixed, thereby limiting the ability to increase the amount of active materials within the cell.
Another approach taken to increase the service performance of a cell is to utilize additives within the electrodes of the cell. For example, U.S. Pat. No. 5,599,644 discloses the use of SnO.sub.2, and other similar materials in the cathode. Another example is disclosed in PCT/CA92/00553, having International Publication No. WO93/12551, entitled "CATHODES FOR ZINC MANGANESE DIOXIDE CELLS HAVING BARIUM ADDITIVES." This reference teaches the use of a barium compound additive such as barium sulfate (BaSO.sub.4) in an amount of 3% to 25% in the cathode of an electrochemical cell. The aforementioned U.S. Patent and PCT publication are both hereby incorporated by reference. The additives discussed in both references provide for enhanced service performance. Despite past increases in the service performance, the need to find new ways to increase service performance remains the primary goal of cell designers.